In order to contribute to the review process designed to generate specific recommendations for the fifth revision of the Diagnostic Statistical Manual of Mental Disorders (DSM-V), American Psychiatric Association (APA) held the The Future of Psychiatric Diagnosis: Refining the Research Agenda conference series, collaborating with the World Health Organization (WHO) and the United States National Institute of Health (NIH). Dimensional Models of Personality Disorders: Refining the Research Agenda for DSM V is the second of two reports on personality disorders derived from one conference in the series, "Dimensional Models of Personality Disorder: Etiology, Pathology, Phenomenology, and Treatment". The monograph provides insight into the research process behind decisions on the classification "personality disorders." It is composed of nine articles, each followed by commentaries.

It is immediately apparent that this is an attempt to reach expert consensus about the dimensional models of personality disorders, not a bid to ground claims about personality disorders in the actual experiences of patients. The commitment to scientific credibility seems to be perceived primarily as a commitment to research in the natural sciences such as genetics and molecular neurobiology, not a reflection of the accurate and true experiences of patients and families. Accordingly the amount of data acquired from clinical cases is limited, while there is extensive reference to research in genetics, molecular neurobiology, etc. In the following, I summarize the main themes of the collection and address a few of my concerns.

The current diagnostic approach in the DSM-IV represents a categorical perspective; it lists personality disorders as "qualitatively distinct clinical syndromes" and places them on a separate diagnostic axis (DSM-IV-TR, p.633). Each personality disorder is regarded as consisting of a series of categorical phenomena, with persons being either cases or non-cases of the disorder. In other words, upon encountering a patient, the clinician determines whether his/her symptomatology is sufficiently close to a particular diagnostic category to warrant a diagnosis. Personality disorders listed in Axis II of the DSM-IV include Paranoid Personality Disorder, Schizoid Personality Disorder, Borderline Personality Disorder, Narcissistic Personality Disorder, among others.

The authors of Dimensional Models of Personality Disorders: Refining the Research Agenda for DSM V seem to agree that the current model has the following constraints: (1) Excessive diagnostic co-occurrence: in the current schema, the maladaptive personality functioning of patients cannot be described by a single diagnostic category because, as some studies indicate, many patients meet the diagnostic criteria for more than one personality disorder. (2) Inadequate coverage: the existing list of personality disorders does not cover the range of the symptoms encountered by each person. (3) Heterogeneity within diagnoses: studies show significant differences between people who share the same personality disorder diagnosis, which means that each diagnostic category has a heterogeneous class of symptoms. (4) Arbitrary and unstable diagnostic boundaries: the existing threshold for personality disorder lacks a compelling justification for what is considered as abnormal. (5) Inadequate Scientific Base: most disorders listed in the DSM-IV have research programs and clinicians uniquely devoted to understanding their etiology, pathology, and treatment -- this is not the case for personality disorders.

These criticisms lead to an alternative proposal which defends classifying personality disorders as dimensions of general personality functioning that underlie and cut across existing diagnostic categories. Among the many attempts to identify fundamental dimensions of normal and pathological personality, an influential one frequently cited in this collection is Five Factor Model (FFM). FFM defines five dimensions of personality: openness, closedness, extraversion, antagonism, and neuroticism. Maladaptive variations on the scale of each personality trait are believed to be the source of different personality disorders.

The articles in the report discuss FFM and other dimensional models in terms of their descriptive capacity and clinical utility. Discussions frequently appeal to research from behavioral and molecular genetics, as well as the research that investigates the relationship between neurobiological mechanisms and personality disorders. Topics include childhood antecedents of personality disorders, cross-cultural issues, the continuity of Axis I and II mental disorders, coverage and cutoff points for diagnosis, and the clinical utility of classification. By their inclusiveness, the editors underline that the field is open to alternatives to improve the validity of basic concepts in classifying personality disorders; further, they hope such discussions will influence the creation of the DSM-V.

In "Neurobiological Dimensional Models of Personality: A Review of Three Models," Joel Paris reviews three dimensional models of personality disorders. One is the Cloninger model where dimensions of temperament are linked to a specific neurotransmitter system. In this model, novelty-seeking attitude is linked to dopamine, while harm voidance is linked to serotonin (Cloninger 1987). For Paris, while these kinds of approaches may bear fruit, they may also provide ambiguous data. He suggests that our understanding of brain mechanisms is at a very infantile stage. Until we know more about the neuroscience of emotions and behaviours, attempts to develop a neurobiological model of personality disorder are premature.

The dimensional models of personality disorders developed in the report are not themselves exempt from the limitations of the categorical model. The authors leave many fundamental concepts undefined, such as mental disorder, personal identity, personality trait. Although they appeal to some dichotomies, such as genetic versus environmental factors in discussions of the origins of personality disorders, they do not define these terms.

To cite one example, Thomas Widiger and Erik Simonsen's "Alternative Dimensional Models of Personality Disorder: Finding a Common Ground" describes 18 alternative proposals for the dimensional model of personality disorder. The authors believe that an integrative structure that includes the most important aspects of information from these models will be informative for writers of a future diagnostic manual. They therefore propose five domains of personality functioning: (1) Extroversion vs. Introversion; (2) Antagonism vs. Compliance; (3) Constraint vs. Impulsivity; (4) Emotional Dysregulation vs. Emotional Stability; and (5) Unconventionality vs. Closedness to experience. Each domain is displayed as a bipolar system implying a continuum with normal personality traits. Personality disorders are viewed as maladaptive personality traits in reference to this bipolar system. Widiger and Simonsen consider whether the diagnostic manual should set a standard for normal and adaptive traits or whether it should focus on deviations. Ultimately, they believe that the inclusion of adaptive and normal traits will facilitate the description of each patient's general personality structure and help with the diagnostic process. It will also facilitate the integration of the diagnostic manual with basic science research.

Unfortunately, this article does not successfully deal with the 4th constraint of the categorical classification; i.e., the arbitrary and unstable diagnostic boundaries of the categorical schema remain to constitute a problem for the proposed dimensional model. How would we define the threshold for the personality dimension 5, for instance, "being open or closed to experiences," in the personality domains? My fear is that the boundary between "open" and "closed" personality traits is not easy to determine. The judgment of the degree of openness of one's personality depends very much on social and cultural standards. Even if questions are standardized in defining the properties of an open personality, their cross-cultural interpretations may vary. This may become an insurmountable challenge when a particular personality dimension is taken as a reference to determine whether a person has a personality disorder.

Further to this, in "Personality Dimensions across Cultures," Juri Allik reviews studies of the cross-cultural variation of personality traits. The popular psychological assessment instruments originally developed in English have been translated into numerous languages and are now commonly used throughout the world. Most of these translations make the tacit assumption that the core pathological constructs assessed by the measures substantively transcend human language and culture. Thus, generalizibility is presumed rather than demonstrated. Some take a different point of view, believing that personality disorders are cultural products and derive their meaning from distinct cultural traditions. But Allik suggests current data point to the "psychic unity of humankind at least with regard to underlying personality dispositions." Citing some studies, he states there is more justification today than there was 10 years ago for agreeing with the hypothesis that the pattern of co-variation among personality traits is universal and extends across language and cultures. To a certain extent, the data cited by Allik address my concerns. Yet I am not sure whether these studies are directly relevant to the application of the models of personality dimensions to psychopathology. I would be interested in seeing more research on cross-cultural comparisons of psychiatric samples pertaining to personality disorders. Before replacing the categorical schema with a dimensional model, we need to make sure that the model is applicable to psychopathology.

John Livesley's "Behavioral and Molecular Genetic Contributions to a Dimensional Classification of Personality Disorder" summarizes existing behavioural and molecular genetic research on personality disorders. Livesley argues for an etiologically informed dimensional classification of personality disorder. As he sees it, current personality disorder diagnoses are not natural kinds that "carve the nature at its joints" but artifactual kinds, or conceptual constructs used to organize clinical information. The challenge in constructing a dimensional alternative is to construct a system based on natural kinds. This is an achievable goal, in his view, because genetic research may help taxonomic endeavors by providing information about the etiology of personality disorder.

Livesley does not say what he means by "natural kinds" but his position implies that personality disorders have an underlying "micro-structure" that leads to the prevalence of certain maladaptive personality traits. To support the argument for a genetically informed nosology, he cites evidence that genetic factors have an extensive influence on personality disorder, and that behaviors used to classify individual differences arise from genetic influences. While he addresses one concern when he attaches personality to genetic factors, he ignores the role of environmental factors. Even though he acknowledges the behavioral genetic research that highlights the importance of environmental factors, he suggests that the use of diagnostic classification based on genetic divergence may be preferable, as it would facilitate biological investigations.

Despite its emphasis on environmental and genetic factors, Livesley's article does not define its use of these terms. A position that grounds personality traits on genetic influence must -- at the very least -- define its terms. This is an unresolved conceptual problem with a direct bearing on future classifications of personality disorders, and these will certainly impact the people so classified.

Another article worth mentioning is Robert F. Krueger's "Continuity of Axes I and II: Toward a Unified Model of Personality, Personality Disorders, and Clinical Disorders." Krueger touches on issues regarding the separation between Axis I, containing Clinical Disorders, and Axis II, Personality Disorders. To provide some background, the personality disorders are placed on a separate diagnostic axis because the creators of the DSM-III want to draw clinicians' attention to the presence of maladaptive personality traits. Further, so the thinking goes, an existing personality disorder may have an impact on the manifestation and onset of various Axis 1 conditions. Krueger reviews the evidence for distinguishing personality disorders form other clinical disorders, including include age at onset, treatment response, insight, diagnostic co-occurrence and etiology. These reasons are less than convincing, in his view, as personality and clinical disorders are so interconnected. Future research must seek a better understanding of why and how they are connected, something which can be achieved by integrating mental disorder research with research on the structure of general personality.

The articles in the report focus on the scientific research relevant to dimensional models of personality disorders. Only one article discusses the clinical utility of the dimensional model, namely, Roel Verheul's "Clinical Utility of Dimensional Models for Personality Pathology." Verheul emphasizes the importance of assessing the clinical utility of the dimensional model of personality disorder in addition to its diagnostic validity. Defining the clinical utility as the diagnostic criteria's capacity of fulfilling the various clinical functions of a psychiatric classification system, he addresses such issues as conceptualizing diagnostic entities, communicating clinical information, choosing effective interventions, predicting future treatment needs, user acceptability and accuracy, professional communication, and clinical decision making.

Dimensional Models of Personality Disorders: Refining the Research Agenda for DSM V is an important book for academics with an interest in the classification of mental disorders, particularly scholars who are curious about the DSM-V creation process.

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